SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '561212c5f1ff1a92b9f9f94dd09b883819a673fa06f274035ff2abd4b3da8b17' 
  AND token = 'svrWKKHSbQAtrAtPLF5ZaCYL6iVJ5bBm8NXvW6Nmr/Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}